1. Field of Invention
The invention relates generally to cooling of the brain, brain stem and associated tissues during trauma, or periods of decreased blood flow to reduce or prevent neurologic injuries thereto due to ischemia and anoxia. More particularly, the invention provides an apparatus and corresponding method for cooling of the brain, brain stem and associated neurologic tissues and maintaining them at a temperature sufficient to slow metabolic rates of the brain, brain stem and associated tissues a sufficient amount to reduce or prevent neurologic injuries thereto due to ischemia and anoxia. With the invention, the victim recovers with increased chances of survival and less chance of permanent brain damage.
2. Description of Related Art
When an ischemic or anoxic injury occurs, the brain is deprived of freshly oxygenated blood. For example, this situation typically occurs during cardiac arrest, respiratory arrest, stroke and other cerebrovascular trauma, suffocation, drowning, strangulation, electrocution, toxic poisoning (carbon monoxide, cyanide, etc.), metabolic insults or other similar trauma. Without a steady supply of freshly oxygenated blood, the brain ceases to function and after resuscitation, most patients will suffer some damage to the brain and associated neurologic tissues.
For example, among cardiac arrest victims overall less than 10% survive neurologically intact and without significant brain damage. The other approximately 90% either die or sustain some neurologic injury from ischemia (i.e., lack of blood flow to the brain), or anoxia (i.e., lack of oxygen to the brain). Such frequency of neurologic injury occurs because after a cardiac arrest, basic cardiopulmonary resuscitation and advanced life support techniques, such as CPR, closed heart cardiac chest massage, and electroshock treatments, typically require fifteen to twenty minutes to regain circulation from a failed heart. Reversible neurologic damage begins as early as four minutes and irreversible neurologic damage begins as early as six minutes after circulation stops. To combat this potential neurologic injury, initial resuscitation efforts need to be directed toward reviving the brain in addition to resuscitating the heart.
As indicated above, anoxic and ischemic brain injuries from cardiac arrest result in damage to the brain and associated neurologic tissues after about four minutes. In contrast, the heart can survive intact up to four hours after cardiac arrest. The short viability of brain tissue upon deprivation of oxygenated blood is a result of the requirement of high amounts of nutrients for tissue maintenance. Brain tissue uses almost all of the nutrients supplied by the circulating blood for maintenance and stores only a small amount of nutrients. Absent blood flow to the brain, the small amount of stored nutrients is rapidly exhausted. Once exhausted, brain oxygen content is rapidly depleted. This oxygen depletion is traumatic and causes a series of reactions in the oxygen starved brain tissue cells. These reactions are believed to produce free radical ions, primarily consisting of the superoxide radical O.sub.2.sup.-. These free radicals complex with proteins in the brain and associated neurologic tissues, altering respiration, energy transfer and other vital cellular functions, and irreversibly damage these tissues.
Efforts should be directed toward resuscitating the brain to attempt to extend the period of time the brain can function without oxygen while the patient remains neurologically intact. The medical literature is replete with examples of humans surviving extended periods of time (greater than 5 minutes) without oxygen being delivered to the brain.
Hypothermic therapy is one method of keeping the brain alive absent oxygen. It involves cooling the brain to a temperature where its metabolic activity is decreased. When the brain's metabolic activity is decreased, it uses much less oxygen and stored nutrients are exhausted slowly, while production of irreversibly damaging O.sub.2.sup.- free radicals is slowed and almost completely ceased. Thus, upon resuscitating the body from trauma, the patient emerges neurologically intact. For example, children revived after hours of submersion in very cold water have fully recovered with little if any neurologic damage.
Previous inventions, such as those described in U.S. Pat. No. 5,149,321 to Klatz et al. ('321), U.S. Pat. No. 5,234,405 to Klatz et al. ('405), U.S. Pat. No. 5,261,399 to Klatz et al. ('399) and co-pending U.S. Application Ser. No. 08/447,812 ('812), address the need to direct resuscitation efforts toward the brain, such that the victim can survive ischemic or anoxic trauma neurologically intact. Specifically, the '321 and '405 patents discuss devices and methods for resuscitating the brain such that its metabolism is slowed in order that the victim survive these metabolic insults neurologically intact. The '399 patent and the '812 application disclose a device and method for externally cooling the brain and associated tissues.
Russian Patents Nos. 1138152 ('152) and 904,695 ('695) disclose helmets for treatment of the head with cold or heat. However, the helmets of the '152 and '695 patents are not suited for field use, as they are large structures restricted to clinical facilities. Moreover, they must be used by a skilled surgical team and maintained by skilled technicians and are not disposable. Further, neither of these devices is configured to cool the neck and upper back.
Brain cooling devices, such as those disclosed in U.S. Pat. No. 4,920,963 and Russian Patents Nos. 652,942 ('942), 454,907 ('907) and 446,015 ('015), are complex and require that the patient be placed into the device lying down. The '907 patent discloses using chilled water to effectuate cooling and the '942 and '015 patents are silent as to whether they have the capability of chilling the brain, brain stem and associated neurologic tissues a sufficient amount to reduce or prevent ischemic and anoxic injuries thereto. Further, none of these devices are disposable or suitable for field use due to their structure. Nor are any of these devices configured to cool the neck and upper back.
Various other patent documents disclose apparatus for cooling the head, for example, International Patent Publication No. WO 82/04184 ('184), International Patent Publication No. WO 89/09583 ('583), U.S. Pat. No. 4,753,242 ('242), British Patent No. 2,130,489 ('489), German Patent No. 8607793 ('793), and U.S. Pat. Nos. 3,909,655 ('655) , 3,606,890 ('890), 4,691,762 ('762) and 4,138,743 ('743). These devices cool the head respectively to treat chemotherapy patients suffering from alopecia (hair loss); to treat post-operative plastic surgery patients; to treat patients suffering from migraines; or merely to provide a beauty treatment or for personal comfort. However, these devices are not capable of providing the cooling sufficient to slow metabolic rates of the brain, brain stem and associated tissues a sufficient amount to reduce or prevent neurologic injuries thereto due to ischemia and anoxia. Further, these devices are generally complicated, designed for clinical use, not disposable and are not configured to cool the neck and upper back.